Questions & Answers about Компания арендовала здание на десять лет.
Why do we need the preposition на here? Couldn't we just say Компания арендовала здание десять лет?
In Russian, you use на + Accusative case to show the intended duration of the result of an action (how long the lease is meant to last). If you left out на and just said десять лет, it would mean the action of leasing itself took ten years to complete (i.e., the company spent ten long years just trying to sign the paperwork!).
If на requires the Accusative case here, why is the word лет in the Genitive case?
The preposition на only directly affects the number десять. Because десять is a number, its Accusative form looks exactly like its dictionary form. However, Russian grammar rules state that numbers 5 and higher always force the noun that follows them into the Genitive plural. So, лет is in the Genitive plural because of the number десять, not because of the preposition на.
Why is the word for years лет instead of a plural form of год?
The word год (year) has an irregular Genitive plural form: лет (which historically meant summers). You must use лет after numbers 5 and higher, which is why it pairs with десять here. If the lease had been for 3 years, you would use the Genitive singular of year: на три года.
Здание is the direct object being leased. Why didn't its ending change to show the Accusative case?